Electrical alternators adapted for use in motor vehicle applications typically include a rotor assembly rotatable within an annular stator. Rotor pole pieces, which may preferably be of an interleaved “claw pole” design, rotate with the rotor shaft, while the stator itself includes a stator core defining radially-extending slots in which a plurality of stator windings are disposed. An excitation winding is carried within the cavity formed between pole pieces of the rotor, and a DC signal is applied to the excitation winding through a pair of slip rings and associated brushes. The magnetic field produced by the winding interacts with the pole pieces to create an alternating polarity magnetic field which, upon rotation of the rotor assembly as driven by the vehicle's engine, induces current flow in the stator windings in a known manner.
Because the resistance of the conductors of the stator windings is inversely proportional to alternator output and efficiency, the resistance and therefore the cross sectional area of the stator winding is an important factor for improving alternator output and efficiency. To achieve higher electrical outputs while reducing the overall size of the stator, the prior art has, therefore, sought to employ stator conductors of square or rectangular cross-section to increase conductor cross sectional area and, hence, improve the performance and efficiency of the dynamoelectric machine. Such wire can be laced into the stator core winding slots in a very densely packed configuration, thereby improving “slot space utilization.” However, square- or rectangular-cross-section wire is more difficult to form and wind into the stator winding slots, since it is necessary to align the conductor cross-section with the slot.
Designers of stator assemblies further attempt to reduce or eliminate the need for providing electrical conductor terminations and connections in the stator assembly. The necessity to physically connect conductors in the stator core assembly adversely impacts cost and complexity of the manufacturing process. A particular technique for winding continuous conductors onto a stator core is disclosed in U.S. Patent Application Publications No. 2003/0137205A1 and No. 2003/0137204A1, each assigned to the assignee of the present invention, which disclosures are hereby incorporated by reference. In these published patent applications, a high-slot-fill, multi-phase stator winding is provided in which each phase is defined by a pair of interleaved conductors that alternate radial positions in each of an adjacent pair of winding layers as the conductors together traverse the core's circumference, except in the “radial shift” areas in which each conductor transitions radially inwardly to together form the next winding layer. The radially-inward winding layer pairs are then inserted atop the first winding layer pair to advantageously provide a stator winding featuring radial-aligned and, therefore, sequentially-inserted winding layers (each of which is defined by pairs of interleaved conductors).
While the above technique thus advantageously provides a radially-aligned layered stator winding, it will be appreciated that the interleaved conductors forming each winding layer pair continues to present manufacturing challenges. Accordingly, there exists a need for a method of forming a multilayered, cascaded stator winding that does not require interleaved conductors.